Sapphire
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| Sapphire | |
|---|---|
 The 423-carat (85 g) blue Logan Sapphire | |
| General | |
| Category | Oxide mineral |
| Formula (repeating unit) | Aluminium oxide, Al2O3 |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol: (32/m) |
| Space group | R3c |
| Identification | |
| Color | Typically blue, but varies |
| Crystal habit | As crystals, massive and granular |
| Fracture | Conchoidal, splintery |
| Mohs scale hardness | 9.0 |
| Luster | Vitreous |
| Specific gravity | 4.0~4.1 |
| Optical properties | Abbe number 72.2 |
| Refractive index | nω=1.768–1.772 nε=1.760–1.763, Birefringence 0.008 |
| Pleochroism | Strong |
| Melting point | 2,030–2,050 °C |
| Fusibility | Infusible |
| Solubility | Insoluble |
| Other characteristics | Coefficient of thermal expansion (5.0–6.6)×10−6/K relative permittivity at 20 °C ε = 8.9–11.1 (anisotropic)[1] |
Sapphire is a precious gemstone and a variety of the mineral corundum (α-Al2O3), It is usually blue, but natural "fancy" sapphires also occur in all other colors other than red as red colored corundum is called ruby.[2] The variety in color is due to small amounts of elements such as iron, titanium, chromium, copper, or magnesium mixed in.
References
- ↑ Harman, Alang Kasim; Ninomiya, Susumu; Adachi, Sadao (1994). "Optical constants of sapphire (alpha-Al2O3) single crystals". Journal of Applied Physics 76 (12): 8032–8036. Bibcode 1994JAP....76.8032H. doi:10.1063/1.357922.
- ↑ Lua error in Module:Citation/CS1 at line 379: attempt to call method 'match' (a nil value).